. Bulletin of the Department of Agriculture. Agriculture; Agriculture. BULLETIN L480, . Dl PAB1 mi in H IK I ^ PES 01 I'l PECTfi ther common defect—lin^r distortions, j > i t * - J1 pockets. gum roots, black check, staining, and pith flecks are often caused by in» or associated with insed attack. Such defects, however, are not nl- \\;i\ - necessarily caused by insects. DBFB4 n 'I iSSI D it UNO DiSToanoNS (Characteristic distor- tions and abnormalities in the annual rings of i pees result from defolia- tion by Leaf-feeding in- sects, as well as Erom other causes, as pointed out by Elart
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. BULLETIN L480, . Dl PAB1 mi in H IK I ^ PES 01 I'l PECTfi ther common defect—lin^r distortions, j > i t * - J1 pockets. gum roots, black check, staining, and pith flecks are often caused by in» or associated with insed attack. Such defects, however, are not nl- \\;i\ - necessarily caused by insects. DBFB4 n 'I iSSI D it UNO DiSToanoNS (Characteristic distor- tions and abnormalities in the annual rings of i pees result from defolia- tion by Leaf-feeding in- sects, as well as Erom other causes, as pointed out by Elartig, Harper, and Craighead! \8). 1 de- struction of the leaves at certain periods causes a reducl ion in the normal amount of food manu- factured by the tree, with consequent loss in the amount of wood laid on and the formation of incomplete annual lay- ers or double rings (false rings). Many species of trees are subject to defoliation, though little is known of the resulting effects except in a few cases. Larch, fir, spruce, jack pine, lodgepole pine, western ye 1 1 o w and white pines, hem- lock, ak, hickory, ca- talpa, birch, and cherry are some of the trees subject to frequent or periodic Fig. 30.—A and B, two views showing small " pitch pocket" or " bird's eye," caused by larva of a fly in western yellow pine KVSV, DISTORTIONS CAUSED BY DEFOLIATION BY THE BUD WOBM Defoliation by the bud worm-9 on spruce and fir produces the first year a decided decrease in wood on the upper stem, while an abnormally larger ring is laid on at the base. In subsequent years a gradual reduction occurs, the narrowest ring being laid on some four or five years later throughout the tree. Gradual increase then 20 Cacoecia (Harmologa) fumiferana Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the orig
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